This invention relates to a control system for controlling the operation of a refrigeration system, particularly an automotive air-conditioning system, to maintain a cooled space at a constant desired temperature.
Air-conditioning systems for automotive vehicles, such as automobiles, trucks and buses, are subject to widely varying operating conditions (for example, heat loads and compressor speeds), and are usually inefficient in that their system capacities do not always match their loads. Such inefficient operation wastes energy and significantly affects the vehicle's fuel consumption. The control arrangement of the present invention, on the other hand, controls the operation of a refrigeration system in a unique way so that the system capacity is regulated to just meet the needs of the vehicle compartment to be cooled. By maintaining a correct balance between system capacity and refrigeration load at all times, no energy is wasted and fuel economy is enhanced.
Moreover, with the present invention the evaporator pressure is maintained as high as possible while still satisfying the heat load requirements, thereby minimizing the discharge pressure/suction pressure ratio across the compressor. Since the power needed to drive the compressor is directly proportional to the ratio of the discharge pressure relative to the suction pressure, maximizing the evaporator preesure (and thus the suction pressure) permits the compressor to operate at maximum efficiency.